This invention pertains to the aldol condensation of acetone to produce isophorone and mesityl oxide. More particularly, this invention pertains to the use of a catalyst for the aforesaid purpose prepared by the deposition of a calcium salt on particular alumina supports followed by calcination.
The gas phase aldol condensation of acetone at high temperatures to give a variety of products including mesityl oxide, isophorone, mesitylene, phorone, and 3,5-xylenol is well known in the art. The processes are complicated by the inability to obtain a single product and especially the presence of numerous low value high boiling materials.
Numerous conventional, strongly basic heterogeneous catalysts such as magnesium and calcium hydroxide are known. For example, U.S. Pat. No. 2,183,127 describes the vapor phase condensation of acetone in the presence of CaO or Ca(OH).sub.2 catalyst at 350.degree. C. to 400.degree. C. to give isophorone in 25% yield, U.S. Pat. No. 2,393,510 claims the vapor phase condensation of acetone over sodium or calcium aluminate at 424.degree. C. and a liquid hourly space velocity of 0.35 hr..sup.-1 to get 15% acetone conversion and a yield of about 43% isophorone, 32% mesityl oxide and 25% higher boiling products. The use of other bulk oxide and mixed oxide catalysts are described in several references for the condensation of acetone to isophorone, viz., U.S. Pat. No. 4,086,188; U.S. Pat. No. 4,165,339; U.S. Pat. No. 2,549,508; British Pat. No. 909,941; British Pat. No. 1,010,695 and U.S. Pat. No. 2,451,350. Only a few disclosures have been made for the use of Al.sub.2 O.sub.3 or metal oxide(s) supported on Al.sub.2 O.sub.3. These include U.S. Pat. No. 2,429,361; U.S. Pat. No. 2,425,096; U.S. Pat. No. 2,419,142 and H. J. Seebald et al. Archive der Pharmazie, 406, 305(6) (1972). However, the efficencies to a desired product, e.g., isophorone achievable by this process are barely satisfactory and far less satisfactory in respect to the acetone conversion achieved per pass. Also, the above heterogeneous catalyst when employed as vapor phase catalysts either require high temperature (350.degree. to 400.degree. C.), are of short life and/or tend to be fragile which provides a more expensive process. The co-precipitated mixed oxide catalysts have the drawback of exhibiting poor catalyst manufacturing reproducibility and are expensive.
It is, therefore, an object of this invention to provide long life, regenerable solid catalysts for the process of aldolization of acetone to yield chiefly isophorone and mesityl oxide.
It is a further object that the aforesaid catalyst operate in an heterogeneous system.
It is still another object that the process lend itself to the aldolization and dehydration of acetone in the vapor phase over a fixed catalyst bed.
It is still a further object of this invention that isophorone and mesityl oxide are produced in high conversion per pass.
It is another object of this invention that the catalyst used can be manufactured reproducibly and economically.
Other objects will become apparent to those skilled in the art upon a further reading of the specification.